The separation of close boiling point components, or the separation of organic isomers is important for a variety of petrochemical processes. The use of adsorption separation processes has enabled the normally very difficult separation of components in a mixture. The adsorption separation process for a large scale process uses the simulated moving bed design for a continuous separation of components in the mixture. The simulated moving bed process is described in U.S. Pat. No. 2,985,589 by Broughton et al. The simulated moving bed process uses a simulated countercurrent movement of the adsorbent with the fluid mixture to be separated.
The process is performed using established commercial technology wherein the adsorbent is placed in a plurality of adsorbent beds and between each pair of adsorbent beds are access ports for admitting and withdrawing fluid from the system. As the process progresses, the streams involved in the process are shifted from one adsorbent bed to the next adjacent adsorbent bed. Normally, there are four streams, a feedstream comprising the mixture to be separated, an extract stream comprising the preferentially adsorbed component, a desorbent stream for displacing the adsorbed component, and a raffinate stream comprising the remaining components of the feedstream mixture. Each stream is shifted simultaneously and in the same direction along the adsorbent beds. With each shift in location, fluid is delivered or removed from a different bed. With this progression, the preferentially adsorbed component is separated from the mixture.
Many aspects of the adsorption separation process must be considered. For a given separation, the process can be a molecular sieving process, or in other cases, the process can be a separation due to electrostatic forces. The general process relies on the differential adsorption of the different components in the mixture. One, or more, component(s) is preferentially adsorbed, and the remaining components are swept along as the fluid continues to flow over the adsorbent. A particular separation also needs to consider the type of adsorbent material used, and operating conditions, as well as appropriate desorbents that can be used.
Adsorption separation uses expensive equipment, and the equipment is not readily replaced to increase the production of a product stream. With increasing demand for the products from adsorption separation processes, increasing the throughput, capacity and recovery of the products is desirable without having to replace the equipment.